After a cocktail
or beer, the body converts the alcohol to acetaldehyde and thence to
acetic acid, or vinegar, which is used for energy in the body. Half
of all Asians, however, have a genetic mutation that cripples the enzyme
 aldehyde dehydrogenase  that converts acetaldehyde to acetic
acid. This leads to an accumulation of acetaldehyde in the blood, which
is associated with several types of cancers and other illnesses, including
late-onset Alzheimer's disease. Acetaldehyde also dilates the blood
vessels, leading to flushing.

What Ames and Elson-Schwab
discovered in the literature is that the mutation, a change in only
one amino acid, occurs in an area of the enzyme that binds to the cofactor
NAD (nicotinamide adenine dinucleotide), resulting in a 150-fold decrease
in binding between enzyme and cofactor and a subsequent decrease in
the conversion of acetaldehyde to vinegar.

NAD comes from
vitamin B-3, niacin, suggesting that high doses of niacin might boost
the activity of the enzyme/coenzyme complex and help to prevent the
build-up of acetaldehyde resulting from alcohol consumption among Asians,
Ames said.